The History and Science of the Barrel- Lesson 9: Rum Transformation Inside the Barrel

Lesson 9: Rum Transformation Inside the Barrel

Modern Day Alchemy

The sugarcane alcohol is in the barrel, patiently awaiting for “aging” to take place. What exactly will happen and how long will it take? Describing what will happen is relatively straightforward, but defining how long it takes is much harder. There are many variables to consider: type of wood used, type of char or toast, the aging warehouse’s climate and, last but not least, the type of alcohol the barrels are filled with (light, medium or heavy).

What the alcohol will lose as it is converted into rum:

• Very light (volatile) alcohols will be the first ones to evaporate. These alcohols are thinner and more easily absorbed and perspired through the oak staves.

• Because of the above, the proof of the alcohol will decline with the passing of the years. The highest loss will come in the first year, and losses after the second or third year will level out, as long as the barrel remains structurally sound and as long as the warehouse manager has a good practice for topping off barrels regularly (once to twice a year).

• Some aromas will be lost, especially when aging in charred oak barrels, due to the odorabsorbing effect of the inner surface carbon.

What the alcohol will gain as it is converted into rum:

• Light to dark amber color. Toasted barrels will take longer time to impart color, while charred barrels will do so faster.

• Tannins. French Oak barrels that are toasted light to medium will impart the highest concentration of tannins. Charred American Oak barrels will take the longest.

• Other wood extractives will be delivered to the rum, resulting in increased mouth complexity and prolonged aftertaste. Lighter char levels tend to show more fruit esters and spice notes while darker char levels will extract more vanilla flavors and color into the rum.

• Complexity. The aromas and flavors mentioned in the previous bullets will continue to react with the oxygen inside the barrel, transforming into additional compounds.

When we stop to carefully analyze each and every step described above, it is hard not to compare the aging of rum to modern day alchemy (the art of transforming base metals into gold).

Our special thanks to Independent Stave Company for their support in our research of oak.